1. Field of the Invention
The present invention relates to a control system for an industrial plant. Such control systems have one or more display devices for displaying information relating to the plant, and the present invention is particularly concerned with such display devices. The present invention also relates to a method of controlling an industrial plant.
2. Description of the prior art
Most complex industrial plants have at least one control with displays for displaying information about the operation of the plant, to enable an operator (the user of the control) to monitor the performance of the plant. It is frequently the case that a single display (such as a CRT, VDU, or large-size screen) is arranged to display several different bits of information, corresponding to different parts of the plant, for example, in practice, the control system stores one or more patterns representing the plant, which forms the basis of the display. Those patterns are made of a plurality of pattern elements, such as symbols representing pumps, valves, and lights for interconnecting them so that the pattern represents the plant. Furthermore, the control system receives plant data representing operating conditions of the plant, such as temperature or pressure at particular points, whether valves are open or closed, whether a pump is running or not, etc. The plant data is then combined with the patterns in a way which is preset, to form one or more prepared displays. The operator may then select one of those prepared displays, and display it when needed, or the apparatus may be arranged to display sequentially all those prepared displays.
At its simplest, the designer of the control system determines which plant data is to be displayed with a given pattern, so that the prepared patterns are entirely preset, and there is only one prepared display corresponding to each pattern.
However, such a system has a disadvantage. If the operator of the system is relatively inexperienced, it is often helpful for the display to display all the plant data relating to the part of the plant corresponding to a given pattern. Furthermore, explanatory information can also be displayed. The display then becomes complicated because the relative inexperience of the operator requires that complex information.
However, if the operator is already experienced, or an inexperienced operator learns more about the system, it then becomes less important for some of the plant data to be displayed. Then, the very complexity of the display tends to reduce the efficiency of the operator, because there is the risk of the operator becoming confused by the volume of information that is displayed. It is preferable, then for a simpler display to be provided, in which only that information which is actually necessary or desired by the operator is displayed.
Japanese patent application laid-open 55-157009 seeks to solve this problem. It proposes that more than one prepared display is provided for a given pattern (e.g. corresponding to a particular part of the plant). Then, one of those prepared displays may be relatively complete, for an inexperienced user, and another may be more simple for an experienced user. The operator then can switch between one prepared pattern and another, depending on his level of experience.
Furthermore, Japanese patent application laid-open number 55-157009 also suggests that, for a given pattern, several prepared displays may be provided, each displaying different conditions, e.g. one displaying temperature conditions corresponding to the pattern, another displaying pressure conditions corresponding to the pattern, etc., so that the operator may select a particular group of plant data for observation.
In Japanese patent application laid-open number 55-157009, however, every display that is to be displayed has a corresponding prepared display, i.e. a different prepared display is needed for each particular manner of presentation. Thus, it may be desired to have one display of a particular pattern showing a large amount of information, and this will need one prepared display, and a the further prepared display will be needed if that pattern is to be displayed with a more limited amount of information. The number of prepared displays is therefore large. Since a large amount of programming work (up to 3 days) may be required to produce each prepared display, the total amount of work is therefore large. Furthermore, a large memory is needed to store all the prepared displays.